45 normal volunteers and 40 glaucoma patients (known visual field defects)with equal sex distribution between the ages of 40 and 80 will be recruited for this study by H. Grady Rylander, M.D. at The Eye Institute of Austin and grouped by age into the following categories: 40-49, 50-59, 60-69, 70-79. Every effort will be made to equalize the number of patients in each age category and to recruit volunteers representing the race distribution in our community. Maps of RNFLT, phase retardation, and RNFL birefringence will be acquired from individuals within each age category.